1. Field of the Invention
The present invention relates generally to systems for supporting building structures on a relatively unstable base. In particular, the present invention relates to an adjustable pier system for supporting a residential home on unstable soil.
2. Brief Description of the Prior Art
Unstable soil poses many challenges in the construction and maintenance of building structures, such as residential homes. In particular, structures built in areas of unstable soil frequently experience foundation and wall cracking due to soil subsidence. It is well know that available methods for repairing/replacing cracked foundations and walls are very expensive.
In certain relatively flat regions prone to flooding (e.g., the Mississippi River Delta), many homes and other building structures are built on piers. These piers (typically formed of brick or cinder blocks) are used to raise the elevation of the structure above certain flood levels, without having to re-grade the entire lot. Buildings constructed on piers generally employ sill beams, which rest on the top of the piers and support the load-bearing walls and floor trusses of the structure.
Some conventional pier-supported buildings are constructed with the piers sitting directly on the soil. In such a case, each pier is highly prone to elevational and/or lateral shifting over time. Other conventional pier-supported buildings are constructed with the piers supported on spread footings. Spread footings are typically formed of a square pad (e.g., 4′×4′×10″) of reinforce concrete. Spread footings help temper settling of the piers by spreading the vertical load over a larger area of the soil. However, each of these spread footings is still prone to shifting as the soil subsides.
In areas known for highly unstable soil (e.g., the Mississippi River Delta) many homes and other building structures are supported by a pier on grade beam system. In such a system, relatively large reinforced concrete grade beams are placed in the ground under each exterior and interior supporting wall of the home. The individual grade beams are physically connected with one another to form a unitary base for supporting the home on the unstable soil. The piers are placed on the grade beams and used to support the main structure of the home on the grade beam. However, even when grade beams are employed, soil subsidence can cause the grade beams to tilt and/or crack over time. When this happens, expensive measures must be taken to repair and/or re-level the home. Typically, the home is leveled by adjusting the elevation of the grade beams and/or by adjusting the height of the piers. Using conventional methods, both these operations are very expensive and dangerous.